Treatment of artificial silk



Patented Sept. 12, 1939 UNITED STATES 2,172,516 PATENT OFFICE TREATMENT OF ARTIFICIAL SILK No Drawing. Application August 20, 1937, Serial No. 160,190

5 Claims.

. parts thereof.

In the manufacture of artificial silk it is the ultimate object to produce a thread that has a high uniformity of strength, denier, dyeing and shrinkage properties. Such thread is particularly adapted for use in the production of artificial silk fabrics having an improved uniformity of quality. In the older methods of processing freshly spun artificial silk thread the said thread was reeled into skeins and thereafter purified and dried under no tension. These older methods, therefore, were satisfactory from the standpoint of the quality of the finished product, but the complicated operations involved therewith made these processes commercially undesirable.

During the evolution of the artificial silk industry the trend was to eliminate as many processing steps as possible in order to cut down on the cost of production. It is generally conceded at the present time that the most practical method for the after treatment of freshly spun artificial silk is to purify and dry the same in package form. The principal objection, however, is the uneven shrinkage or contraction which takes place in the package when it is wettreated and dried in this form. There are several patented processes which seek to overcome such shrinkage differences; i. e., one such process involves the collection of the thread on a substantially rigid imperforate bobbin or spool, wher-eafter it is purified and dried on the bobbin, rewound onto another spool and again wetted out and dried. The theory in this procedure being that the inner layers of thread lying adjacent the rigid core of the original bobbin prevents any substantial contraction and, in effect, produces some stretching upon drying, while the outer layers can contract to a higher degree. Upon the rewinding, rewetting and redrying on the second support, the relative position of the layers of thread being reversed, a compensating shrinkage takes place. The Moritz Patent No. 1,967,252 discloses an analogous method except that the thread is rewound and twisted on a tapered spool. The package is next removed and placed on a core of'smaller diameter than the inner circumference of the package, wet treated and/or bleached and dried thereon.

Another patented method for equalizing the shrinkage differences in packages of artificial silk produced by the centrifugal spinning method is disclosed by the Moritz Patent No. 2,074,232. As distinguished from the bobbin spinning process these types of packages are spun and twisted simultaneously into a rapidly rotating centrifugal pot or bucket. There is no internal support in packages of this type. However, certain shrinkage and contraction differences also normally occur during drying unless a special method is employed. In the Moritz Patent No. 2,074,232 the drying medium is restricted entirely to the space defining the thread-free interior thereof. During the course of the drying operation the threads dry progressively from the inner layers to the outer layers so that as the inner layers dry and contract, space is created progressively toward the outside in order that the outer portions can substantially contract.

It has been determined that despite the compensatory methods now in existence, there is a certain amount of thread which has not been permitted suificient contraction and, therefore, is not usable for weaving yarn. In this respect packages of artificial silk produced in accordance with the centrifugal method and those produced according to the bobbin spinning method are analogous to some degree. More explicitly, a package of artificial silk which has been rewound and twisted onto a tapered spool and removed therefrom stil1 contains several thousand yards of thread on the outside which is inferior. This thread is that which was originally wound on a rigid holder in a semi-plastic condition. Referring to the cakes of silk spun in a centrifugal bucket, we have also determined that the outer layers containing several thousand yards of thread are not of the best quality.

As previously stated, past practice to improve this condition has involved one or more wetting and drying operations throughout the entire bodies of the silk packages. In each of the drying operations, however, regardless of how the dehydration operation is conducted, the extreme outer portions of the packages are in contact with the atmosphere and a substantial amount of moisture evaporates causing a drying thereof. These outer layers are prevented from contracting to the same extent as the inner portions because of the resistance offered by the still wet and swollen inner layers. In other words, even though the so-called inside outside drying method is employed, the outer layersnever have ample opportunity to adequately contract. When utilizing the inside outside drying method the drying medium is confined to the interior of the packages and by evaporation removes the moisture progressively from the inside to the outside. As the inner layers dry and contract, space is created progressively to the outside to permit contraction progressively to the outside, thereby effecting uniform shrinkage and contraction. However, as stated before, in the extreme outermost portions, evaporation takes place during the initial drying operation thereby preventing the same degree of contraction as in the remainder of the package. This defect in the process always results regardless of the number of wetting and drying operations and might more clearly be expressed by stating that the shrinkage of the outermost portions never catch up to the shrinkage of the other parts of the package.

It is, therefore, the object of the present invention to introduce an additional step in order to obtain a package of artificial silk threads having extremely uniform shrinkage characteristics throughout the entire bodies of the said packages.

It is further contemplated by our improved method to cause the extreme outer layers of thread in twisted packages to fully contract upon drying.

The fiow sheet indicates generally the usual treating operations, to which both bobbin and cake spun packages are subjected. As shown therein, cakes are formed from thread simultaneously spun and twisted, while the bobbin packages must be twisted after collecting, purifying and initially drying. Purified wet cake packages and dry bobbin packages are subjected to the same type of pressure bleach treatments and thereafter hydrmextracted, deformed and dried. The final novel step that is contemplated by the present invention is moistening and redrying the extreme outer layers only, in the packages as designated in the said flow sheet.

In carrying out our process with reference to bobbin spun silk we generally follow the method disclosed by the Moritz Patent No. 1,967,252. The thread is spun and collected on a perforated or foraminated bobbin and subjected to the usual purifying steps consisting of washing, desulphurizing and drying on the said bobbin. The thread is then rewound and twisted onto'a tapered spool, covered with a cloth sock and transferred together with the covering to a foraminated spool having a diameter less than the inner diameter of the thread package. The bobbin spun package is not as solid as that of the cake and for this reason requires an insert for the subsequent rewetting and bleaching operation. The thread package is pressureor vacuum-bleached with or without an internal support and thereafter dried in an apparatus of the type disclosed by the Moritz Patent No. 2,074,232. The bobbin spun package is now in a condition substantially the same as that of a package which has been spun and twisted into a centrifugal bucket, washed, desulphurized and dried as shown in the flow sheet. If it is desired, prior to the drying step the wet package may be transferred to a polygonal insert such as that described in the Sunderland Patent No. 2,058,368 and hydro-extracted, thereby simultaneously deforming the same.

The dried twisted packages are now in a condition specified in the foregoing description and ,normally the outside several thousand yards of thread are of inferior quality. We have determined by investigation that if this particular portion of the thread package could be moistened so as to acquire from forty to one hundred per cent. of moisture (calculated on the bone-dry weight) while at the same time maintaining the remainder of the package substantially dry, then on subsequent re-drying, the extreme outside layers would have the same degree of shrinkage as the rest of the package. In applying our invention we moisten or dampen the outermost layers by spraying lightly with water. We have found it advantageous to apply the moisture in the form of a very fine spray so that the moisture will penetrate a number of layers of thread near the outside of the package comprising a few thousand yards without excess wetting of the extreme outside layer. The package may then be dried normally, but we have found that the best results are obtained if this final drying is conducted in steps, i. e., the package is first dried for several hours at a high relative humidity, for example, 80% or over, and thereafter dried normally. The moistening itself may be effected by conditioning the package in an atmosphere of very high relative humidity, 80% or more, instead of by spraying. Preferably, when the humidifying step alone is employed, cover plates are used on the top and bottom of each package, which causes the moisture to contact the outermost layers of thread only. After conditioning for several hours, the packages are dried normally. The thread package now possesses uniform shrinkage characteristics throughout, and every part thereof may be successfully used for all textile purposes.

It is apparent that various modifications may be made in our invention without departing from the spirit and scope thereof and the inventive concept must be limited only as set forth in the appended claims.

What we claim is:

1. A method for treating artificial silk which has been first collected on a circular holder in package form which comprises the steps of washing, purifying and drying thepackage on the said holder, rewinding and twisting the threads onto a second support thereby reversing the order of the layers of thread, removing the package from the support and completely wetting out and drying and finally moistening the outer surface only of the package and drying.

2. A method of treating artificial silk' threads and the like comprising the steps of wet treating the originally formed package to remove impurities therefrom and drying, rewinding and twisting the thread into package form, transferring the package to a foraminated spool having a diameter smaller than the inner diameter of the package, bleaching and redrying the package, moistening the outer surface only of the package by spraying and finally drying said surface.

3. A method as defined by claim 2 wherein the moistening of the outer surfaces of the packages is effected by spraying.

4. A method as defined by claim 2 wherein the moistening of the outer surfaces of the packages is effected by conditioning the packages in an atmosphere of relatively high humidity.

5. A method of after treating dried twisted artificial silk threads in package form, the outer convolutions of which have been unable to shrink to the same extent as the inner layers thereof which comprises moistening the outer surfaces only of the package so that the outer layers of thread will acquire from forty to one hundred per cent. moisture and thereafter redrying the same.

ADRIAN J. L. MORITZ.

WILLEM J. D. VAN DOBBENBURGH. ALFRED E. SUNDERLAND; GILBERT I. THURMOND.

CERTIFICATE OF CORRECTION. Patent No.-2,l72,5l6. September 12, 1959.

- ADRIAN J. L. MORITZ, ET AL.

It is hereby certified that error appears in the above nfimbered patent requiring correction as follows: The sheet of drawing as shown below shofild be inserted as a part of the Letters Patent; in the heading .to the printed specification, line 8, strike out the words and period "No Drawing.";

p 93 A. J. L.- MORITZ :17 AL' 2,172,516 TREATMENT OF ARTIFICIAL SILK Filed Aug. 20, 1957' menu :pmvmw 12mm swam/mum COLLECTED 101v JPU/V M0 TW/JTED mum/mm: bone/1v //v PACKAGE/018M //v ,4 CENM/Fl/ML But/(Er fimorio ,q/vo TWISTED aw'm .sECO/Y0 6. 001.

and that the said Letters Patent shouldbe read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of October, A. D. 1959.

Henry Van Arsdale, Acting Commissioner of Patents.

(Seal) 

